The economic disposal of waste solids and recovery of clean water from aqueous solutions and dispersions thereof is a recognized problem. Also, the need to recover clean water and valuable solid materials from aqueous solutions and dispersions thereof is a common occurrence. Ideally, apparatuses and processes for the recovery of water from aqueous solids should provide ease of disposition of all constitutents, avoidance of pollution, economic operation and hygienic handling, and should, in addition, yield clean water. Furthermore, in the course of recovering clean water it is desirable to obtain by-products, both solid and liquid, which are either valuable in themselves or can be utilized to further the economics of the process. For purposes of this invention it is to be understood that the term "aqueous solids" is employed generically to include suspensions, dispersions, solutions, mixtures and other forms of fluid association of solids in water.
In our U.S. Pat. No. 3,855,079 titled "Process and Apparatus for Recovering Residual Oil from Solids Dehydrated in an Oil Medium and Grossly Deoiled" are described process and apparatus whereby aqueous solids are admixed with a relatively non-volatile fluidizing oil to form a mixture which is dehydrated by heat evaporation. The substantially anhydrous solids in fluidizing oil slurry thus formed is thereafter separated into the oil phase and the solids phase. However, the solids have sorbed thereon appreciable amounts of fluidizing oil which contaminates the solids and which will be lost to the process and contribute to unfavorable economics if not recovered. Accordingly, the fluidizing oil-laden solids are subjected to a subsequent extraction step using a relatively volatile, water-immiscible light oil. The light oil-laden solids are then brought into direct contact with blowing steam to effect removal of the residual water-immiscible light oil from the solids.
In our U.S. Pat. No. 4,270,974 titled "Process and Apparatus for Recovering Clean Water and Solids from Aqueous Solids" are described process and apparatus in which aqueous solids are mixed with a low viscosity, relatively volatile, water-immiscible light fluidizing oil to form a mixture which is subjected to dehydration by heat evaporation whereby substantially all of the water and at least part of the light oil are evaporated and subsequently recovered. The light fluidizing oil is then largely separated from the solids. The solids, carrying residual light fluidizing oil, are brought into direct contact with blowing steam to cause removal of the residual light fluidizing oil therefrom.